Introduction

This volume is the sequel to Normal Aging: Reports from the Duke Longitudinal Study, 1955-1969. Its purpose is to bring together and summarize the main findings which build upon and extend those presented in the first volume. It contains all the reports from the Duke Longitudinal Studies published since 1969 as well as an almost equal number of papers presented at professional meetings or written especially for this volume. These reports present new findings on aging among the older longitudinal panel as well as the first findings on the middle-aged panel.

Both of these volumes deal with "normal aging" in two senses: healthy aging and typical aging. The aged and middle-aged persons studied were relatively healthy in that they were noninstitutionalized, ambulatory, community residents who were willing and able to come to the Duke Medical Center for one or two days of tests and examinations. Second, the more common or typical patterns and problems of aging are focused upon rather than the unusual abnormalities. This volume deals with the typical physical changes that accompany aging, typical health care patterns, typical patterns of mental aging, some common forms of mental illness among the aged, the normal social roles, self concepts, satisfactions, leisure and sexual behavior, and the overall factors related to longevity.

As pointed out in the first volume, investigations of normal aging are of crucial importance in advancing the science of gerontology and in helping aged persons develop and enjoy a richer and longer life. When we can distinguish normal and inevitable processes of aging from those which may accompany aging simply because of accident, stress, maladjustment, or disuse, we can better focus our attention and efforts on those factors which can be changed and corrected.

Both volumes also emphasize the theoretical and methodological advantages of the longitudinal and interdisciplinary methods used in these studies. Since aging is by definition a process of change over time, it would seem that the best way to study aging is longitudinally, by repeated observations over time. This is not meant to deny the value of cross-sectional studies, nor to deny the technical and methodological problems connected with longitudinal study, but it is meant to reassert the unique advantages of longitudinal studies such as the following: each panel member can be used as his own control, consistent trends can be distinguished from temporary fluctuations, errors due to retrospective distortion are minimized, early warning signs of disease or death can be studied, cohort differences can be distinguished from age changes, and the effects of one kind of change on another kind of change at a later time period can be studied.

The interdisciplinary nature of the study is useful because aging affects many interrelated types of behavior and functioning. When specialists from different disciplines work together, the mutual stimulation, correction, and combination of perspectives can result in more accurate, thorough, and comprehensive understanding of the aging process.

However, this sequel differs from the first volume in several respects. While most of the reports in the first volume were previously published elsewhere, this sequel contains fifteen original papers written especially for this volume or presented to professional meetings but not published elsewhere. Second, while the first volume was limited to reports from the first longitudinal study of aging (persons over 60 years of age), this sequel is about one-third devoted to reports from the Adaptation Study of middle-aged persons (46-70 years of age). Third, this sequel shows that the tempo of reports produced has increased, because it contains thirty-five reports produced in the past four years (about nine per year) compared to the fifty basic reports in the first volume which were produced during the preceeding fourteen years (about three and one-half per year).

The reader who is interested in detailed description and discussion of the first longitudinal study of aging is referred to chapter 1 of the first Normal Aging volume. Suffice it to say here that the first longitudinal study of aging began in 1955 with 271 persons 60-90 years of age. The subjects were not a strictly representative sample, but were selected from a pool of volunteers who lived in the community so that the overall sample reflected the age, sex, ethnic, and socioeconomic characteristics of the older population in Durham, N.C. Each panelist was brought in to the Medical Center for a two-day long series of medical, psychiatric, psychological, and social examinations. These examinations were repeated every three or four years until 1965, every two years until 1972, and since then the examinations are being repeated on an annual basis. In 1973, the eighth round of examinations on the survivors of this study was completed.

The second longitudinal study, or Adaptation Study, was begun in 1968 with 502 persons 46-70 years of age. These panelists were a random sample of the members of the local health insurance association stratified by age and sex. The sample and study was designed so that at the end of five years there would remain approximately 40 persons in each of ten five-year age-sex cohorts. This design makes possible various kinds of cross-sequential types of analyses in order to separate the effects of aging from cohort differences and from changes in the environment over time. Each subject was brought in for a one-day long series of physical, mental, and social examinations. The panelists are reexamined at two-year intervals and in 1973 the third round of examinations was completed. For more details and discussion of the adaptation study design, the reader is referred to Appendix A in this volume.

The articles which are reprinted by permission from various journals are presented with no deletions except for duplicate passages such as those that repeat the description of the panelists. Deletions of a sentence or more in these articles are indicated by ellipses, and minor changes have been made for uniformity. Since most of the reports are interdisciplinary, the placement of some reports in one chapter rather than another was somewhat arbitrary, but an attempt was made to group reports by the type of central variable under investigation. Each chapter first presents the reports from the first longitudinal study and then reports from the Adaptation Study. Brief summaries of the reports introduce the chapters, and the book closes with an overall summary of the main findings and themes. The reader may wish to start with these summaries in order to decide which reports to read in more detail.

We appreciate the cooperation of the many authors and journals or publishers for their permission to reprint their articles. Special thanks are due to Mrs....